An increasing number of electronic components are used on printed circuit boards and the like. A large number of these are being miniaturized such that the electrical contact members are smaller and more closely spaced. Since the majority of these components are soldered to circuit boards, and then cleaned in an aqueous or solvent cleaning process, there is an increasing need to have the components sealed to prevent solder, fluxes, cleaning solvents, and moisture from entering the components and causing malfunctions. These components must have assemblies that will not be affected by the soldering temperatures and cleaning conditions required during the manufacturing process.
In addition, the electrical contacts of such components are often subjected to stress both during and after manufacture. The components are often made by molding a dielectric composition over a prestamped electrical circuit means by insert molding and other methods as known in the art. The electrical circuit means have a plurality of electrical contact members, at least a portion of which extend outwardly from the overmolded housing and form an interface with that housing. The electrical contact members may then be subject to additional stress by subsequent forming of the extended contact members, other manufacturing steps and inserting the component onto a circuit board or other mounting surfaces. It is desirable that the seal at the interfaces be able to withstand insertion forces exerted by automatic insertion equipment.
U.S. Pat. Nos. 4,417,106; 4,531,030; 4,600,971 and 4,611,262 disclose typical components wherein the electrical contacts must remain sealed at the interface of the metal contact members with the housing despite stress being applied to the contact members during forming, other manufacturing steps, and insertion into circuit board or other substrate.
U.S. Pat. Nos. 4,417,106 and 4,531,030 disclose DIP switches comprised of a sealed electrical contact assembly and contact-actuating mechanisms latchably secured thereto. The contact assembly is comprised of a dielectric frame molded over a plurality of electrical contact members. The contact members have electrical terminal sections which extend outwardly and downwardly from the frame. U.S. Pat. Nos. 4,600,971 and 4,611,262 disclose electrical circuit packages comprised of dielectric housing members molded onto lead frames. The housing members in these patents include a plurality of openings therein for receiving and interconnecting leaded and leadless components respectively with contact sections of the lead frame.
When making electrical components such as those described above, it is desirable that sealing engagement be maintained at the interface or joint between the molded housing and the extending electrical circuit means even when the extended circuit means are subject to stress induced by forming or insertion forces. It is desirable that the sealing engagement be maintained when the component is subjected to the high temperatures associated with soldering. It is also desirable that the sealing engagement at such interfaces be resistant to solder, fluxes and solvents to prevent such from being wicked into the molded housing and contaminating or damaging the contact area.
While crystalline or semicrystalline molding materials may be used to form the housing members of the components, it has been found that the housing does not completely seal around the metal circuit members or will develop microcracks or separate at the metal/housing interface when the components are subjected to stress at the joints or interfaces of the housing and circuit members. These stress induced separations permit entrance of solder, flux, cleaning solvents and the like into the contact area, which could render the component electrically useless. Generally, stress induced microcracks are not readily discernable upon visual inspection. Heretofore, effective sealing has been achieved by the use of thermoset materials as the dielectric housing members. Since these materials must be cured for a period of time prior to removal from a mold, the mold cycle time is relatively long compared to that required for thermoplastic materials. It is desirable, therefore, to use materials that will allow shorter cycle time.